136kHz Direct Conversion Receiver by IK2PII
I describe a simple direct conversion receiver, thinked for QRSS and DFCW communications, as companion of ARGO or SPECTRAN programs. The receiver is useful also as portable receiver, fast turn-on receiver for a quick look an the band or as very low cost (and performances) spectrum analyzer.
http://www.qsl.net/ik2pii/lf/dcrx136.htm

136kHz Converter door PA3GZC
Omdat mijn HF-transceiver (30kHz. - 30MHz.) op de nieuwe 136 kHz. banderg ongevoelig is, heb ik een converter gebouwd dat met een locale X-tal oscillator op 10.000 MHz. omhoog mengt naar 10.136 MHz.
http://www.a63.org/cqfrwden/jrg13/feb-99/136kc.htm

136 kHz one knob QRSS receiver by IK2PII
I don't like knobs, pushbuttons, blinking leds and so on whistles and bells on the receivers front panels. For digital modes the ideal receiver must be very simple, front end selectivity, manually adjustable gain, IF filter. All the goodies you can find on the HF receivers can be done by software.
http://www.qsl.net/ik2pii/lf/okqrssrx.htm

Active Loop Converter for the LF Band by VK5BR
In the converter which is described, a loop antenna is used as the only tuned inductive element with positive feedback applied to increase its effective Q and sharpen up its tuning. This of course is the old trick called reaction or regeneration used in the early days of TRF receivers to improve selectivity.
http://users.tpg.com.au/users/ldbutler/ActiveLoopConverter.htm

An electro-mechanical RX for VLF by MØBMU
Historic VLF station "SAQ" was put back on the air on 17.2kHz for a day of special transmissions on 1st July 2001. This inspired Jim Moritz, M0BMU, to construct an appropriate receiver for the event....
http://www.wireless.org.uk/mechrx.htm

A LowFER Receiver Using a "Software" IF by KØLR
This article describes a "software" receiver that uses a simple, low cost hardware downconverter in conjunction with sound-card software such as DL4YHF's "Spectrum Lab" or I2PHD's "SDRadio", which act as a tunable DSP-IF system.
http://www.qsl.net/k0lr/SW-RX/sw-rx.htm

"Passive converter" using HCMOS switch by SM6LKM
This converter uses a 74HC4053 as the mixing element. It simply reverses the polarity of the incoming RF at the local oscillator rate. The principle is the same as in the case of diode ring mixers.
http://home4.swipnet.se/~w-41522/lfconv/lfconv.html

Ricevitore VLF Valvolare by IWØBZD
Il circuito di seguito descritto è stato appositamente progettato per tale scopo. La sua caratteristica innovativa è proprio quella di poter funzionare con una unica tensione continua di 12 V e poter essere all’occorrenza alimentato con una piccola batteria NiCa o Pb di quelle utilizzate in genere per i flash professionali o antifurti. Il circuito, in queste condizioni, è in grado fornire, dato il suo esiguo assorbimento di corrente, molte ore di funzionamento.
http://www.qsl.net/iw0bzd/VLF_TUBE_RX.htm

Soundcard Receiver by G4WGT
I was inspired by the soundcard receiver which Stefan DK7FC designed...
... I finally built a receiver for use in place of my trusty JRC.
http://myweb.tiscali.co.uk/wgtaylor/LF%20&%20MF%20Experiments%2017.html

VLF/LF to 28.5 MHz Receiving Converter by DF3LP
This converter is one of my early projects. It is built using "ugly style" in a small metallic case usingBNC for in- and output connection including some internal shielding of the crystal oscillator.
http://www.qsl.net/df3lp/projects/lfconv/index.html

VLF nach KW-Konverter durch DG7XO
Dieser Converter stammt von der Homepage http://www.radiosky.com ab.Ich habe dazu ein Layout für ein OM aus unserem OV gemacht, dass ich auch hier zur Verfügung stellen möchte.
http://www.dg7xo.de/selbstbau/vlf2kw.html

136kHz L.F. Pre-amplifier by GØMRF
This circuit is based on a design by Dave Pick G3YXM and was jointly redesigned in 2003 after the original coils and polystyrene capacitors were made obsolete.
http://www.g0mrf.com/preamp.htm
 

Loop Pre-amp for LF by G3YXM
If you want to use a a small multi-turn loop on LF, you will find that the sensitivity is not good enough to receive the weaker signals. A good preamp for a loop needs to have a high input impedance and good signal handling characteristics (to prevent cross-modulation).
http://www.wireless.org.uk/circuits2.htm#loopamp

Pre-amp/filter for 136kHz by G3YXM
Most modern tranceivers cover LF but the performance is not always very good. All you can hear are strange whistles and burbles which aren't really there! You need this little circuit. It has a gain of about 10dB and a nice sharp band-pass response about 3kHz wide, enough to cover the 136 band.
http://www.wireless.org.uk/circuits2.htm#preamp

Field strength meter for the 137 kHz band by PAØSE
The power radiated by an antenna is equal to the radiation resistance multiplied by the antenna current squared. Measurement of antenna current can be done in the 137 kHz band by for instance a thermocouple ammeter or other means.
http://www.wireless.org.uk/pa0se.htm